I am done growing height wise but I'm scared because I'm pretty short so what if I get fat? I can not let that happen.

How old are you?
Just because you're short does NOT mean your going to be fat..
If you're overweight now, it just means your metabolisms slow and you have to work extra hard to lose that weight
It's not too bad, just tone up

Hun, how old are you? What makes you think you will get fat just because you think you have stopped growing? Just being short does not mean you are going to get fat. There are plenty of short skinny people in this world.